This invention relates to condensation polymerization and, more particularly, relates to condensation polymerization in the vapor phase of aromatic polyamides.
The formation of aromatic condensation polymers is well known in the art. For example, Hill et al., U.S. Pat. No. 3,006,899, and Kwolek et al., U.S. Pat. No. 3,063,966, disclose the preparation of a wholly aromatic high molecular weight polyamide by reacting an aromatic diamine with an aromatic diacid halide in a solvent with an acid acceptor present. The polymers have an exceptionally high melting point and are useful for many purposes, including films and fibers.
Lindlof, U.S. Pat. No. 3,607,365, discloses a vapor-phase technique for the preparation of polyurethanes and polyureas by the reaction of isocyanates with alcohols or amines. Neither reaction liberates any reaction by-product. Lindlof's method involves alternately exposing a substrate to vapors of the isocyanate and then the amine or alcohol until a polymeric coating is built up. Lindlof stresses that his reaction takes place on the substrate surface by first one compound being adsorbed or reacted thereon and then the next compound reacting with the ends of the molecules of the first compound which are oriented perpendicularly to the substrate surface.
Various articles have appeared in the Russian journal "High Molecular Weight Compounds" about polycondensation reactions to form polyamides. An article by Sokolov et al. in 1961 describes preparation of linear polyamides by the reaction of diamines with diacid chlorides in a "gas-phase" synthesis, described as more particularly a liquid-gas interface reaction. In an article by Sokolov in 1964, the foregoing method was described as having produced polyamides such as those from p-phenylene diamine and oxalyl chloride (a partially aromatic polyamide). In 1965, Bagramyants et al. reported gas-gas polycondensation reactions of aminoethanoic acid with hexamethylene-diamine adipate.